The invention relates to a confocally chromatic sensor and a method for determining coordinates of at least two different determination locations of at least one measurement object. The present invention relates in particular to the field of coordinate measuring technology using a non-contact coordinate measuring machine.
Various devices and methods for determining coordinates of at least two different determination locations of a measurement object, in particular of an extensive measurement object, are known from the prior art. By way of example, methods for topography measurements such as, for example, triangulation methods, deflectometry or stripe projections are known. These methods can be used for whole-area measurements over relatively large regions into the square meters range. However, accuracies required for coordinate measuring technology, for example into the nanometers range, cannot be achieved by means of such methods.
Confocal and confocally chromatic distance sensors, so-called confocally chromatic point sensors, are furthermore known. In the case of such sensors, a depth determination is carried out by means of an evaluation of an intensity distribution along a distance coordinate z, also called height coordinate. Confocally chromatic sensors make it possible to measure the distance coordinate z with a single image. In principle, in the case of such sensors, use is made of measurement objective lenses having chromatic aberration, which focus portions of a light beam with different wavelengths in different focal planes along an optical axis of the sensor. Each wavelength of the light beam can thus be assigned a distance coordinate. If a focus of a wavelength is situated on a surface of the measurement object, an intensity maximum can be measured for said wavelength on a sensor element of the confocally chromatic sensor and the depth can thus be determined.
However, a measurement of an extensive measurement object by means of such sensors can necessitate a significantly longer measurement duration. Moreover, when scanning a surface of the measurement object, such sensors have to be moved accurately with respect to said surface. Furthermore, confocally chromatic sensors are generally expensive, large and heavy. Integration into an existing optical system can be difficult, moreover, since imaging metrology usually has a good chromatic correction. In particular, existing optical systems attempt to avoid an imaging aberration which is the basis of the confocal chromatic sensor. Furthermore, by way of example, front lenses and/or a lens system of confocally chromatic point sensors are not suitable for an areal imaging.
Therefore, it is an object of the present invention to provide a chromatically confocal sensor and a method which at least largely avoid the disadvantages of known devices and methods. In particular, the intention is to enable a determination of distance coordinates of at least two different determination locations of at least one extensive measurement object.